It's not really an either-or situation - the designation does both at once. When a site gets that status, countries commit to actual conservation standards and management plans, which means restricted building, protections for ecosystems, and enforcement mechanisms that weren't there before. At the same time, yeah, there's the prestige angle and the tourism boost that comes with it, but that funding and international attention is what actually makes the protections stick. Mount Olympus already has some protections as a national park, but UNESCO status ups the ante and gives Greece leverage and resources to maintain it properly long-term.